The proposed work is an exploration of the use of affinity methods for the assay of arachidonate metabolites and as physiological probes. We propose to extend present studies of polymer-tethered 15-(3H)-PGF2 alpha as reagents for the assay of PGDH (an enzyme metabolizing prostaglandin) and the natural prostaglandins themselves. A number of novel assays for prostacyclin are proposed. These include biological ones and the group will also prepare 100 ci/mmole PGI2 for studies of platelet receptor affinity. Videofluorometric detection will be applied to the following: HPLC and TLC detection of prostaglandin bearing fluorescent markers, and to the detection of 3H/14C ratios in assay methods based on radiotracers. Prostaglandin E2 levels will be determined in diabetics during insulin withdrawal by RIA, videofluormetric GLC, and confirmed by a new GC/MS assay in which 18,18,20-trimethyl-PGE2 (obtained by total synthesis) serves as the carrier and internal standard.